Cups on arms, cups on effector?

I'm looking to make a large delta, similar to the DC42 build. I'm looking at 8/6mm (OD/ID) carbon arms, with 6mm cylindrical magnets slotted inside and some form of cup to keep the magnet slightly separated from the 10mm balls placed on the effector. I'm probably going to start with printed cups, but later may machine some delrin cups as this shouldn't be too difficult to do.

Basically my question is, does this sound like a good idea? Most people seem to have the balls on the arms, and this certainly seems to simplify things as magnetic cups are easier to source. Based on some comments I've seen, having the cups on the rods does seems to make disconnects less likely though, and gives for a wider range of movement over the surface area of the balls.

Having the cup on the arm is easier to get the 45 degree placement for the ball on the effector , the other way around its more complicated, I bet every example of magnet on the effector are flat magnet not in 45 degree, and if you can, you want to have your ball on effector and carrier at 45 degree.

Having the magnet inside the carbon I dont think its a good idea, see they say 6 ID but must of the time the carbon will not be exactly 6 ID so you will have to sand it down if smaller and sanding carbon if you can avoid is the best. So magnet inside the cup ( you can machine the ID very tight for the magnet so no glue to hold them) and cup glue to carbon is so far the best magnetic design I seen.

Here a hint : Get them machined right away its a critical part of a good working printer and when you design your cup say 60 degree where the ball sit, make sure the ball go through the entire cone and past a little, so when you put your magnet you back them up a little till you get no contact. If your ball are not going deep enough you cant push the magnet further and you have big gap trouble and loss of holding force. What I say is dont try to machine a gap, back your magnet to make one.

My experience is I've tried k800 unmodified which have magnetic cups on effector and carriages, but on the effector the angle of magnets to effector is 0. They disconnect under modest jerk/acceleration. I modified them by changing the angle to 45 degrees. It helped.

Then I ordered a set of arms/balls from Haydn Huntley. These have magnets in the arms with Delrin cups at the end. On the effector/carriages are the balls. These can be at 45 degrees depending on carriage/effector used but don't have to be with the magnets in the arms. They have not disconnected yet even at high acceleration and speed. Worth every penny. Sure you can make some but they are very well made and precise.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

How much did it cost to get the Haydn arms all in? They look good, but the cost is putting me off when I could easily make them myself for a lot cheaper...

About $85 but I paid £17 customs to the UK.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions

Haydn Charged me $27 plus carriage for a set of Balls and Delrin ends and I can't recommend them highly enough they are simply Superb.

Yes you can print rod ends but the Machined Delrin ones just ooze Quality and will have lower friction than PLA or ABS Ends they take 10mm Diameter magnets Haydn's preferred ones are 10x15 N50 grade ones.

Well worth the expense IMHO only reason I went for the Ends and Balls is I needed much longer arms.

Doug